Television antenna



Aug. 30, 1955 J. M. KANE TELEVISION ANTENNA Filed May l5, 1952 INVENTOR.dames /1/1, Kane 4 MEMBER 0F THE FYROM 2,716,703 Patented Aug. 30, 1955United States Patent Olice 2,716,703 TELEVISION ANTENNA James M. Kane,Los Gatos, Calif. Application May 15, 1952, Serial No. 287,902 1 Claim.(Cl. Z50-33.51)

This invention relates to a parasitic array of the Yagi type. Moreparticularly, it relates to an antenna which is suitable for use infringe area television reception of a number of channels.

It is one object of the present invention to provide a multiple bandantenna which signal strength making it suitable for use in televisionfringe areas.

i In the drawings forming a is illustrated nels 4, 5 and 7 as they arenow designated by the Federal It will be obvious to those skilled in theart that the same principles may be em- K' bodied in antennas suitablefor reception of any desired channels and that more than three channelsmay be combined in a single antenna. In the description of the inventionfrequent reference will be made to the receiving properties of theantenna but it is obvious that the same principles may be embodied in atransmitting antenna.

Turning now to the drawings which form a part of this application thereis shown in Figure l a perspective View of my improved televisionantenna.

In Figures 2 there is shown a detailed view of the method of couplingthe driven element on channels 4 and 5 to the transmission line.

gives a high gain and high all the parasitic elements and the drivenelement for channel 7 on the transmission line.

Referring now to the drawings by reference characters, there is shown inFigure l a television antenna having two parallel spaced bars designated4 and 6 which serve both as a transmission line and as a support for theelements of the antenna. Bars 4 and 6 may be suitably made of thin`walled aluminum tubing having an outside diameter of l inch and spacedl2 inches. Other suitable dimensions may be used, such as 1.25 inchtubing spaced 7.75 inches on centers. With these particular dimensions,the bars v4 and 6 constitute a transmission line having an impedance ofslightly over 400 ohms. Thus, the transmission line consisting of bars 4and 6 provides a good impedance Wire transmission line 8 which has size18 copper Wires spaced 1 inch between center.

Fastening means 10 are provided at one end of the transmission line forcoupling to the open wire line 8. The impedance match is sufficientlyclose to permit ordinary plastic insulated line Twin Lead) to be usedinstead'of the air insulated line illustrated.

The bars 4 and 6 are supported and held in their spaced relationship bya center section 12 which is preferably antenna to a mast 13. of plasticor metal but Center section 12 may be made 1s suitably made with thecenter ter section 12 and for insulating the bars from the centersection 12.

Both the driven and parasitic elements are supported at right angles tothe bars 4 and 6 as is shown in the drawings.

ln the embodiment shown, the antenna has three driven 1/2 inch O. D.aluminum tubing, although other suitahle metals may be used.

The method of fastening these two driven elements to the bars 4 and 6 isshown in detail in Figure 2. The

- surrounded by a suitable insulator such as polyethylene ln Figure 3 isshown a detailed view of the method of coupling the driven element forchannel 4 to the transmission line.

Figure 4 is a detailed view of the method of supporting The capacitanceof such a coupling is about 10 mmfd.

A different method is used for fastening the driven element for channel7 and also the channels to the transmission line.

consists of a metallic ring rial 42. Preferably the ring is made fromattened tubing. The dimensions of this connection are so selected that aconnector has a capacity of about element 32 is connected to thetransmission line capacitatively only.

Having now described the driven elements of the array, the parasiticelements will be described. Located at the front ot' the antenna is thedirector 42 for channel 5. The director is 67 inches long and is spaced29 inches (0.2 wave-length) from the channel driven element 16. It willbe noted that the director 42 is mounted on the transmission line bymeans of wooden rods 44 and 46. These wooden rods serve as insulatorsfor the element 42 and are 8 inches in length. This leaves 2l inches ofthe transmission lines 4 and 6 ahead of the driven element 16, saidlengths acting as matching stubs to match the driven element 16 to thetransmission line. The wooden rods 44 and 46 may be painted withaluminum paint, thereby constituting a resistance element. Such aresistance tends to swamp any currents traveling from the back to thefront of the antenna. Without such a terminating resistance, anyreflected waves picked up from the opposite direction would be reectedback into the transmission line and cause a ghost image. 1n extremefringe areas, the resistance may be omitted. Instead of painting therods,` a resistor may be fastened across the front of bars 4 and 6. Avalve of 200 to 400 ohms is suitable.

The element 48 is 77 inches long and is mounted 33 inches (0.2wavelength) from the elements 16 and 18. The element 48 serves as adirector for driven element 18 and as a recctor for driven element 16.The element 16 also serves as a director for driven element 18. Mountedat the rear of the antenna is element 50 which is 84 inches long andspaced 33 inches from the element 18. The element 50 acts as a reectorfor driven element 18.

Thus, the channel 5 driven element 16 has a director 42 and a reector 43and is provided with a matching open stub which is 2l inches long tomatch it to the transmission line. The channel 4 driven element 18 hastwo director elements 16 and 48 and one reector 50. That portion of thetransmission lines 4 and 6 lying in front of the driven element 18constitutes about 1/2 wave length at the channel 4 frequency and assistsin matching the channel 4 driven element to the line.

The channel 7 elements are preferably mounted on the opposite side ofthe bars 4 and 6 from the elements for channels 4 and 5, as shown. Thechannel 7 driven element 32 is 31.2 inches long and is insulated fromthe transmission line as shown; it has three director elements 52, S25and 54 each of which is 30 inches long. The director clement 52 ismounted 13 inches (0.2 wavelength) from the element 32 and in turn theelement 53 is mounted 13 inches in front of element 52 and element S4 ismounted 13 inches in front of element 53. The reflector for channel '7is the element 56 which is 33 inches long and mounted 13 inches behindthe driven element 32.

40 covered with a plastic mate-y mmfd; the

As has been previously mentioned, the driven element 32 is insulatedfrom the transmission lines 4 and 6 at its point of support and iscoupled to the transmission line by the matching lines 36 and 38 whichin turn are capaci- 5 tatively coupled to the transmission lines. Theelements 36 and 38 are about 28 inches long. The length of theelectrical path from the channel 7 driven element 32 through theconnecting lines 36 and 38 to the channel 4 driven element 18 is about45 inches. This constitutes about 1A wave length for channel 4 andan oddmultiple of a l/i wave length, i. e. 3A wave length, for channel 7. Thisprevents there being interaction between the two elements which wouldresult in one driven element shorting out the other.

Ey capacitatively coupling the driven elements to the transmission linesthere is a minimum interference between the various driven elementswhich are coupled to the transmission lines. Further, the capacitycoupling is such that it orcrs little resistance to the passage of thehigh frequency television signal but oiers a high resistance to thepassage of lower frequencies, such as ignition noise. Thus, bycapacitatively coupling the elements to the line one secures a highsignal strength together with a high attenuation of lower frequencynoise.

it will be noted that the spacing between any driven element and itsparasitic elements is about 0.2 wavelength. By using this separation theQ of the antenna is kept low, giving a broad response to pass on entiretelevision channel.

The antenna of the present invention is a system or method wherebymultiple complete antennas may be coupled through capacitances to acommon transmission line.

1 claim:

An antenna for high frequency use having in combination a spaced rigidtransmission line, said transmission line having at right angles theretomore than one driven element, each of said driven elements being looselycoupled to the transmission line and parasitic elements insulated fromsaid transmission line, said rigid transmission line .U furnishing thesole support for the driven and parasitic elements, and wherein thespacing of one of said driven elements on the transmission line acts asa shorted matching stub for another of said driven elements on saidtransmission line.

Car

References Cited in the tileof this patent UNITED STATES PATENTS2,175,363 Roberts Oct. l0, 1939 2,290,371 Katzin July 21, 1942 2,292,791Minis Aug. 1l, 1942 2,297,329 Scheldorf S pt. 29, 1942 2,477,647 Pickleset al. Aug. 2, 1949 2,624,001 Woodward Dec. 30, 1952

